This application claims the benefit of Japanese Application No. Hei 11-240065 filed in Japan on Aug. 26, 1999, Hei 11-252033 filed in Japan on Sep. 6, 1999, Hei 11-252034 filed in Japanese on Sep. 6, 1999, 2000-183405 filed in Japan on Jun. 19, 2000, the contents of which are incorporated herein.
1. Field of the Invention
The present invention relates to an electronic endoscope having a C-MOS sensor as an image pickup device and an LED for illumination as illuminating means.
2. Related Art
Recently, there are wide applications of an endoscope whereby the celomic viscera, etc. are observed by inserting an elongated inserting portion in the celom and various treatment can be performed by using a treatment tool which is inserted in a channel of the treatment tool according to the necessity. In the industrial field, an industrial endoscope is also widely used for the observation and the inspection of internal defect and corrosion, etc. of a boiler, turbine, engine, chemical plant, etc.
As the endoscopes which are used as mentioned above, there is an electronic endoscope (abbreviated to an endoscope, hereinafter in which an image pickup device such as a CCD for photoelectrically converting an optical image into an image signal is arranged at the distal end portion of the inserting portion. According to the endoscope, an observed image of an observed site which is illuminated by illuminating light that is supplied from a light source device is formed on an image pickup surface of the CCD. The image signal of the observed image which is obtained by photoelectrically converting by the image pickup device is transmitted to a signal processing section of a camera control unit (abbreviated to a CCU, hereinafter) serving as an external device, a video signal is generated, and an endoscope image is displayed on a screen of a monitor, thereby performing the observation.
In order to provide an endoscope apparatus which is made small in diameter, has simple construction, and realizes various higher functions by eliminating a light guide fiber that is made of an optical fiber, there is disclosed an endoscope apparatus having a solid-state image pickup device for image pickup of an observed site at the distal end portion thereof and a surface light-emitting light source for illuminating the observed site in Japanese Unexamined Patent Application Publication No. 8-117184.
Endoscopes which are used for the industrial are used at dangerous places having explosive atmosphere, etc. such as piping of a chemical plant and a gas tank. The equipment used at the dangerous places needs to satisfy at least a safety standard condition such that xe2x80x9cthe DC is equal to 28 V or less, the amperage is equal to 93 mA or less, and the wattage is equal to 0.66 W or less,xe2x80x9d so as to prevent the equipment from becoming an ignition source, etc.
However, the CCDS which are provided in the endoscope have characteristics in that a value of a rising current which is generated in the case of the driving is increased. Therefore, if a problem of a consumption power is solved, the aforementioned condition of the current value is not satisfied, so that a problem remains in the case of the specification which is used at the dangerous places.
The distal end portion has a high temperature due to the heating of electric parts such as a resistor which are provided near the CCDs and the heat of the illuminating light which is supplied from the light source device. There is a problem that the inspection using the electronic endoscope is difficult for pipings, etc. to handle gas which has a danger of firing at a low temperature, e.g., ethyl nitrite whose firing point is 80xc2x0 C. and ethyl nitrate whose firing point is 85xc2x0 C.
If a user who operates the endoscope at the dangerous place observes the endoscope image, the display device itself needs to satisfy the safety standard condition. Therefore, it is troublesome to prepare a special display device corresponding to the dangerous places. Further, when a display device of non explosion-proof type is used, inconveniently, the display device is disposed at a safe region and an observer who sees the display device of the non explosion-proof type has to observe the endoscope image or instruct the operator at the dangerous place, etc.
Recently, observed sites become complicated and manifold in accordance with the development of the endoscopic medical science, the medical scene requires an endoscope in which an image pickup device having pixel construction corresponding to the observed site (for example, depending on the pixel size and on the NTSC system or PAL system). There are also a variety of pipings such as pipings as observed targets having a large diameter and a small one and, therefore, the industrial endoscopes also correspond to various inspection by preparing many kinds of optical adapters which are exchangeably mounted to the distal end portion of the endoscope so as to correspond to the variation in the diameter and the inspecting purposes.
However, according to the conventional endoscope apparatuses, a drive circuit and a signal processing circuit of the image pickup device are fixed and, thus, there is a disadvantage that only the endoscope using the image pickup device of the same kind and the same specification can be used. That is, if the endoscope having a different pixel construction of the CCD or the endoscope having a different length of the inserting portion is connected the CCU, a desired endoscope image cannot be displayed on the screen of the monitor from the image signal which is transmitted from the CCD.
In order to solve the disadvantage, according to an endoscope apparatus disclosed in, for instance, Japanese Unexamined Patent Application Publication No. 63-260527, a plurality of CCUs corresponding to different kinds of endoscopes are prepared and the plurality of CCUs are exchangeably mounted in a video process device, thereby enabling different electric scopes to be used. However, the endoscope apparatus cannot be adapted to an existing endoscope apparatus, in other words, an endoscope of a type such that the CCU is not exchangeable in the video process device and the size of video process device is enlarged.
In order to solve the problem, according to an endoscope system disclosed in Japanese Unexamined Patent Application Publication No. 5-176882, a plurality of endoscopes having different kinds of image pickup devices are connected to a CCU corresponding to at least one of the different kinds of image pickup devices and can be used. According to an image pickup system disclosed in Japanese Unexamined Patent Application Publication No. 7-360, one CCU can correspond to a probe having image pickup devices whose image pickup methods are different, thereby reducing costs.
Moreover, in order to prevent the best endoscope image from being displayed by decreasing the length of a signal cable which is inserted in an inserting portion of the endoscope depending on the differences in the length of the inserting portion and the maintenance and adjustment, etc., the CCU is provided with cable length correcting means corresponding to the change in the length of the inserting portion or the cable length.
However, the cable length correcting means is provided, and the endoscope system or the image pickup system corresponds to the difference of the CCD which is provided at the distal end portion thereof as disclosed in Japanese Unexamined Patent Application Publication No. 5-176882 or 7-360, thereby, the construction of the CCU becomes complicated. Not only does the price increase but also the size increases and, thus, cause a serious problem for the industrial endoscopes which require mobility.
It is one object of the present invention to provide an electronic endoscope which has a small consumption of power and satisfies a safety standard condition at dangerous places.
It is another object of the present invention to provide an electronic endoscope which can be handled by a user at dangerous places while observing an endoscope image.
It is yet another object of the present invention to provide an electronic endoscope which is made small in diameter and has high mobility and by which the observation is performed, thereby obtaining an observed image with a preferable picture quality by desired number of pixels and construction in pixel in accordance with an inspecting situation and an inspecting purpose.
Simply speaking, an electronic endoscope of the present invention has an illuminating section which is provided with an LED for illumination that emits illuminating light to illuminate an observed site and a C-MOS image sensor that has an image pickup surface on which an optical image is formed and outputs a video signal and, therefore, has a construction which is suitable to various observation by changing the combination of the LED for illumination and the C-MOS image sensor.